Organopalladium complexes with bidentate phosphorus and nitrogen containing ligands

Abstract

Organopalladium complexes containing the potentially P, N-bidentate ligands o-diphenylphosphino-N,N-dimethylbenzylamine (PN) and o-diphenylphosphino-@a-methyl-N,N-dimethylbenzylamine (PN}*{) have been studied. The palladium(0) complexes Pd(P@?N){3} (P@?N = PN or PN}*{) have been prepared: the ligands coordinate to the metal primarily through phosphorus, with the amine function coordinating not at all or only very weakly. Oxidative addition of several organic halides to these palladium(0) complexes afforded the corresponding monoorganopalladium(II) complexes Pd(R)(X)(P@?N) in which the donor ligands are P,N-bidentate coordinated. In solution the divalent species possess a Pd@?N bond, and even in the presence of either free ligand, CO or X}-{ there is no evidence for dissociation or displacement of the amine function from the metal centre. Complexes PdMe{2}(P@?N) have been prepared from the corresponding dihalopalladium complexes by treatment with MeLi. Reaction of these dimethylpalladium species with the electrophiles MeI, MeBr and PhCH{2}Br resulted in replacement of one methyl group by halogen. The structures of Pd(Me)(Br)(PN) and Pd(C@?CSiMe{3})(Br)(PN) have been determined by X-ray diffraction studies. Pd(Me)(Br)(PN) crystallizes in space group Cc with a 8.379(8), b 17.363(70 and c 14.818(6) @9. @b 99.34(5)}o{, and Z = 4; the structure was refined to R{f} = 0.030. Pd9C@?CSiMe{3})(Br)(PN) crystallizes in space group P2{1}/c with a 13.478(3), b 10.848(2) and c 19.212(3) @9, @b 102.59(2)}o{, and Z = 4; the structure was refined to R{f} = 0.038. Both complexes have a square planar configuration around palladium, with the organic group (Me, C@?CSiMe{3}) trans to the amine function and the six-membered chelate ring in a boat conformation.